Volume 36, Issue 2, 2017

Hoary Bat

With its distinct salt-and-pepper coloration and luscious glossy fur, the hoary bat may just be the George Clooney of the bat world. But there is more to this bat than just its good looks.

Pop quiz: What small mammal can be found in northern Canada, Hawaii and Panama? Answer: the hoary bat (Lasiurus cinereus). The hoary bat holds the title of the most widespread bat species in the Americas, with a transcontinental range stretching from southeastern Canada to Hawaii.

Courtesy of MerlinTuttle.org

The hoary bat is a migratory bat species, which means instead of spending winter months hibernating in large colonies, this solitary bat migrates to warm winter habitats. Summers are spent concealed in the foliage of mature deciduous and coniferous trees, typically near the edge of a clearing. Their distinct grey-white coloration (for which the bat is named) and furred tail membrane are prime adaptations for its lifestyle of hanging in tree foliage. In fact, hoary bats camouflage themselves as dry leaves by hanging by one foot and using their tail membrane to wrap themselves up – almost as if they had their own little personal sleeping bags!

Hoary bats may fly as fast as 13 miles per hour and as high as 8,000 feet during their long-distance migrations in the autumn and spring, hunting at night for moths, mosquitoes and occasionally other bats.

These bats are not the most social of creatures, preferring to lead mostly solitary lives in the tree foliage. After mating in autumn, females will move to the northern, eastern and central United States to give birth, often to twin pups (rare in bat species) in mid-May to early July. Males remain in the mountainous areas of the western United States.

Though, much like running into George Clooney at your local store, humans have a small chance of ever encountering a hoary bat. These solitary bats seldom enter houses and spend the daylight hours well concealed in the tree foliage. This has given researchers a handicap as they try to study the bats’ behavior.

“Answering questions like, ‘How many bats are there?’ is difficult because you can’t just count them coming out of a cave. As they move around between multiple tree roosts and over long distances it is hard to mark and recapture them,” explains Bat Conservation International Senior Director of Conservation Science Winifred Frick.

“Hoary bats have always been a bit of enigma. They are widespread, but are rarely encountered by bat biologists because of their solitary nature and the difficulty in observing them roosting in trees during the day, even if they may be right over our heads,” echoes Ted Weller, ecologist with the U.S. Forest Service.

Female hoary bats can weigh 40% more than their male counterparts Courtesy of Michael Durham

“New technological developments are allowing us to monitor movements of individual bats, and we are finding that many of these bats make long distance movements on a nightly basis that we wouldn’t have predicted. We are also finding that some hoary bats use torpor during winter in ways that aren’t much different than bats hibernating in caves, despite the fact that they are doing it alone while hanging in a tree,” explains Weller.

Unfortunately, we may be running out of time to discover the secrets of the hoary bat, as the species is facing an increasingly bleak future. Hoary bats are heavily impacted by wind turbines.

Although currently considered common across North America, an estimated 76,000–152,000 hoary bats are killed each year by collisions with wind turbines. Scientists from Bat Conservation International are working with the wind industry, as well as conservation and government partners, to develop and implement solutions to reduce this mortality rate. By changing how wind turbines are managed and developing acoustic deterrents to discourage bats venturing near the spinning blades, BCI has high hopes that the wind industry can be sustainable not only for our climate, but the future of our bat species as well.